Recently, digital integrated circuit technology has been rapidly developed. In particular, integration with the smallest cost is important for memories due to intense price competition. Digital integrated circuit devices such as memories use bonding wires for connection with other circuits. When there is a differential amplifier in integrated circuits, a transformer is required to convert differential output signals into a common mode output signals. As a method of implementing a transformer in the existing integrated circuits, a method of implementing a transformer itself as a transformer device in an integrated circuit or a method of implementing a transformer device outside an integrated circuit and connecting them has been developed.
First, when a transformer in implemented in an integrated circuit, it should be formed on a plane for the features of the integrated circuit, such that the transformer or an inductor occupies a large area in the integrated circuit. Further, the parasitic inductance is very large due to the thickness and length of the metal wire forming the transformer, so a lot of power is consumed when a current is induced in the transformer. Further, when the substrate where the integrated circuit is placed is made of silicon, there is a problem in that current leaks to the silicon substrate due to a current called an eddy current generated due to the material.
When a transformer is implemented outside an integrated circuit, the other device except for the transformer may be integrated and the transformer implemented in the type of SMD. However, an integrated circuit with components except for a transformer integrated and an SMD type of transformer are required to complete a high-frequency circuit. There is a problem, however, in that since steps for completing a high-frequency circuit are further added, the manufacturing cost increases. Further, since the high-frequency circuit is completed by the integrated circuit and an SMD for a transformer, there is a problem in that the entire size increases.
FIG. 1 is a view illustrating the configuration of a transformer using printing lines in the related art. Referring to FIG. 1, the transformer using printing lines includes a substrate 100, first printing lines 110, second printing lines 120, first bonding wires 130, and second bonding wires 140. Accordingly, the printing lines 110 and 120 and the bonding wires 130 and 140 function as a primary coil or a secondary coil of the transformer. In the existing transformers using printing lines, orthogonal printing lines were connected to bonding wires to increase the coil of the transformers. However, when the integrated circuit connected with the transformer is a symmetrical device, there is a problem in that efficiency reduces because the primary coils 110 and 130 and the secondary coils 120 and 140 of the transformer are not symmetric. Further, since all of the primary input/output electrodes 1stin and 1stout and the secondary input/output electrodes 2ndin and 2ndout are far way from each other, there is a problem in that additional printing lines or bonding wires are required for connection with a symmetrical integrated circuit, so the cost increases.